fix(isPostalCode): improve Dutch postal code regex (#2271)

Author: RobinvanderVliet

src/lib/isPostalCode.js

@@ -52,7 +52,7 @@ const patterns = {
   MX: fiveDigit,
   MT: /^[A-Za-z]{3}\s{0,1}\d{4}$/,
   MY: fiveDigit,
-  NL: /^\d{4}\s?[a-z]{2}$/i,
+  NL: /^[1-9]\d{3}\s?(?!sa|sd|ss)[a-z]{2}$/i,
   NO: fourDigit,
   NP: /^(10|21|22|32|33|34|44|45|56|57)\d{3}$|^(977)$/i,
   NZ: fourDigit,

test/validators.test.js

@@ -11925,6 +11925,13 @@ describe('Validators', () => {
           '3950IO',
           '3997 GH',
         ],
+        invalid: [
+          '1234',
+          '0603 JV',
+          '5194SA',
+          '9164 SD',
+          '1841SS',
+        ],
       },
       {
         locale: 'NP',